Spinning method and spinning device

ABSTRACT

A nozzle device for spinning comprising a nozzle, a polymer solution supply means that supplies a polymer solution to the nozzle and ejects the polymer solution from the nozzle tip, and a solvent vapor supply means that supplies a gas containing vapor of the same solvent as the solvent of the polymer solution at least to the vicinity of the polymer solution just ejected, and a spinning method using the nozzle device for spinning. Solidification of a spinning solution is prevented at the nozzle tip from which the spinning solution is ejected.

TECHNICAL FIELD

The present invention relates to a method of spinning fibers including a polymer, comprising a step of ejecting a polymer solution from a nozzle tip, in which spinning is performed while supplying a gas containing the vapor of the same solvent as a solvent of the polymer solution to the periphery of the polymer solution just ejected, and a device therefor.

BACKGROUND ART

In recent years, a molded body such as a sheet containing of nanofibers has been paid attention as a material having properties not possessed by a conventional fiber molded body, due to the magnitude of a specific surface area thereof. As a method of producing such nanofibers (spinning method), an electrospinning method is well known.

The electrospinning method is a method of obtaining a fiber molded body on a collector by supplying a solution obtained by dissolving a polymer in a solvent (dope liquid) to a tip of a dope liquid ejection nozzle, and applying a high voltage between the nozzle tip and an electrode (collector). Steps thereof include a step of dissolving a polymer in a solvent to produce a solution (dope liquid), a step of supplying the dope liquid to a nozzle tip and applying a high voltage, a step of ejecting the dope liquid from the nozzle tip in a direction of an electrode (collector), a step of evaporating the solvent from the ejected dope liquid to form a fiber molded body, an optional step of dissipating the charge of the formed fiber molded body and a step of accumulating the fiber molded body on the collector due to dissipation of the charge.

In the electrospinning method, there is a problem that continuous production should be enabled even when a volatile solvent is used in the dope liquid. In this regard, Patent Document 1 discloses a technology that enables continuous production by enclosing nanofibers being produced with a solvent in the vicinity of a single tubular nozzle in the prior art, wherein the nanofibers produced are physically prevented from adsorption on the nozzle and/or washed using a solvent stream.

CITATION LIST Patent Literature

-   [PTL 1] JP-A-2010-236133

SUMMARY OF INVENTION Technical Problem

The present inventors ascertained that, when a volatile solvent is used as a solvent of a dope liquid in the electrospinning method, in a step of ejecting the dope liquid from a nozzle tip, a Taylor cone (which is generated at a nozzle tip at the time of spinning and has usually a cone shape, wherein liquid droplets are supplied to the nozzle tip and a voltage exceeding the surface tension of the liquid droplets is applied to the liquid droplets, and thus stretches the liquid droplets in a voltage direction) formed at the nozzle tip solidifies, and this solidified product grows with time, which is the cause for deterioration of spinning stability and reduction in the spinning yield, and further for a problem of inability of continuous production. In addition, it has been shown that such a problem is not limited to the electrospinning method, and is commonly generated in a spinning method in which a polymer solution is ejected into the air.

An object of the present invention is to solve such a problem, and provide a method and a device for suppressing solidification of a spinning liquid at a nozzle tip in a spinning method in which a polymer solution is ejected into the air, for example, such as suppression of solidification and growth of a Taylor cone in electrospinning.

Solution to Problems

In view of the above problems, the present inventors intensively made study, and as a result, found out that in spinning equipment, a nozzle device equipped with a means for supplying the nozzle with a polymer solution to be a raw material of fibers and a means for supplying a tip of the nozzle with the solvent vapor of the polymer solution, producing fibers by supplying the nozzle with the polymer solution to be a raw material of fibers while supplying the vicinity of the tip of the nozzle with the solvent vapor of the polymer solution, suppresses solidification of a spinning liquid at a nozzle tip in a spinning method in which the spinning liquid is ejected into the air, and completed the present invention.

That is, the present inventions are as follows:

-   [1] A nozzle device for spinning, comprising a nozzle, a polymer     solution supply means for supplying a polymer solution to a nozzle     to eject it from a nozzle tip, and a solvent vapor supply means for     supplying a gas containing the vapor of the same solvent as a     solvent of the polymer solution at least to the periphery of the     polymer solution just ejected. -   [2] The nozzle device for spinning according to [1], wherein the     device has a double tubular structure part composed of an inner     tube, the inner tube being a nozzle, and an outer tube surrounding     it, and is configured such that a gas containing the vapor of the     same solvent as the solvent of the polymer solution is supplied from     a space between the inner tube and the outer tube. -   [3] A method for spinning fibers containing a polymer, comprising a     step of ejecting a polymer solution from a nozzle tip, wherein     spinning is performed while supplying a gas containing the vapor of     the same solvent as a solvent of the polymer solution at least to     the periphery of the polymer solution just ejected. -   [4] The spinning method according to [3], wherein the gas to be     supplied contains a substance that is in a gaseous phase under the     condition at the time of spinning, and is saturated with the vapor     of the same solvent as the solvent of the polymer solution.

Advantageous Effects of Invention

The advantageous effect of the present invention is that, in a spinning method in which a polymer solution is ejected into the air, solidification of a spinning liquid is suppressed at a nozzle tip for ejecting the spinning liquid. Accordingly, clogging and deteriorated ejection of fiber components at a nozzle tip are alleviated, consequently, spinning stability and the spinning yield are improved, and continuous production becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A general view of fiber production equipment based on an electrospinning method, using a double tubular nozzle as one example of the nozzle device of the present invention.

FIG. 2 A nozzle device having a double tubular structure as one example of the nozzle device of the present invention.

DESCRIPTION OF EMBODIMENT

In the nozzle device of the present invention, as a means for supplying a nozzle with a polymer solution (dope liquid) to be a raw material of fibers, a usual nozzle device in a spinning device for ejecting a polymer solution into the air can be adopted. Additionally, a means for supplying a tip of the nozzle with the solvent vapor of the dope liquid is also not particularly limited, but in the electrospinning method, a means that does not prevent formation of a Taylor cone in a spinning direction at the time of spinning is preferable. For example, as a nozzle, a means having an inner tube for supplying the dope liquid and an outer tube surrounding it can be adopted, wherein the nozzle is configured such that a gas containing the vapor of a dope liquid solvent is supplied from a space between the inner tube and the outer tube approximately in the same direction as the direction of ejecting the spinning liquid from a nozzle. Accordingly, at least a polymer solution just ejected is placed under the atmosphere of the solvent vapor.

In the production method of the present invention, as a step of ejecting the polymer solution from the nozzle tip, a usual method in a spinning method of ejecting a polymer solution into the air can be adopted. Additionally, as a step of supplying a gas containing the vapor of the same solvent as a solvent of the polymer solution at least to the periphery (vicinity) of the polymer solution just ejected, in the electrospinning method, a method that does not prevent formation of a Taylor cone in a spinning direction at the time of spinning is preferable, and for example, a method of blowing a gas containing a solvent of a spinning liquid to the periphery of the spinning liquid to be ejected, approximately in the same direction as the direction of ejecting the spinning liquid from a nozzle can be adopted.

The present invention can be applied to any technique, as far as it is the spinning technique for generating fibers by vaporization, of a solvent from a spinning liquid, and can be used, for example, in an electro spinning method, a solution blow spinning method, or a force spinning method, and inter alia, it can be suitably used in an electro spinning method.

Examples of a kind of a polymer that can be used in the present invention include a variety of polymers that can be dissolved in any solvent, such as polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyacrylonitrile-methacrylate copolymer, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride-acrylate copolymer, polyethylene, polypropylene, nylon-based polymers such as nylon 12 and nylon-4,6, aramid, polybenzimidazole, polyvinyl alcohol, cellulose, cellulose acetate, cellulose acetate butyrate, polyvinylpyrrolidone-vinyl acetate, poly(bis-(2-(2-methoxy-ethoxyethoxy))phosphazene), polypropylene oxide, polyethyleneimide, polyethylene succinate, polyaniline, polyethylene sulfide, polyoxymethylene-oligo-oxyethylene, SBS copolymer, polyhydroxybutyric acid, polyvinyl acetate, polyethylene terephthalate, polyethylene oxide, biodegradable polymers such as collagen, polylactic acid, polyglycolic acid, poly-D,L-lactic acid-glycolic acid copolymer, polyarylate, polypropylene fumarate, and polycaprolactone, biopolymers such as polypeptide and protein, pitch-based polymers such as coal tar pitch and petroleum pitch, and the like.

A solvent of the polymer solution and a solvent used as the solvent vapor are the same, and usable kinds of solvents include, for example, acetone, chloroform, ethanol, 2-propanol, methanol, toluene, tetrahydrofuran, water, benzene, benzyl alcohol, 1,4-dioxane, 1-propanol, carbon tetrachloride, cyclohexane, cyclohexanone, dichloromethane, phenol, pyridine, trichloroethane, acetic acid, N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, 1-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, dimethyl carbonate, acetonitrile, N-methylmorpholine-N-oxide, butylene carbonate, 1,4-butyrolactone, diethyl carbonate, diethyl ether, 1,2-dimethoxyethane, 1,3-dimethyl-2-imidazolidinone, 1,3-dioxolane, ethylmethyl carbonate, methyl formate, 3-methyloxazolidine-2-one, methyl propionate, 2-methyltetrahydrofuran, sulfolane, and a mixed solvent of two or more selected from the group of these solvents.

As a structure of the nozzle having a double tubular structure of the present invention, a nozzle inner diameter is preferably 0.15 to 1.07 mm, and further preferably 0.34 to 0.84 mm. Additionally, an inner diameter of an outer ring of a double tubular nozzle, which is to be a part for ejecting the solvent vapor, is preferably 1.00 to 2.00 mm, and further preferably 1.30 to 1.70 mm. When an inner diameter of the nozzle and an inner diameter of the outer ring are outside the range, it tends to generate a solidified product at the nozzle tip.

A flow rate range of the polymer solution is not particularly limited as far as it is a flow rate in a spinnable range, and the flow rate range can be preferably set in a range of about 20 ml/h.

Regarding the partial pressure of the solvent vapor used, for example, it can be used in a range of ½ or more of the saturated vapor pressure of the solvent, and it is preferable that the solvent vapor is in saturation. When the solvent saturated vapor is outside the range, it tends to generate a solidified product at the nozzle tip.

A gas flow rate of the solvent vapor is preferably 100 to 1000 ml/min, and further preferably 200 to 800 ml/min. When the gas flow rate is outside the range, it tends to generate a solidified product at the nozzle tip.

EXAMPLES [Production Equipment]

FIG. 1 is one example of an entire constitution diagram of fiber production equipment by an electrospinning method using the nozzle device of the present invention. FIG. 2 is a cross-sectional conceptual diagram of one example of the nozzle device of the present invention. In these figures, it is configured that the nozzle device consists of a nozzle and an outer tube thereof, wherein the nozzle is connected to a device for supplying a raw material solution of fibers, the outer tube is connected to a device for supplying the solvent vapor of the raw material solution, the raw material solution of fibers is ejected from the nozzle, and the vapor of a solvent of the raw material solution is released from a space between the nozzle and the outer tube so as to surround the ejected solution.

[Preparation of Polymer Solution for Spinning]

One part by weight of a polylactic acid-glycolic acid copolymer (PURAS ORB PDLG5010 manufactured by Corbion PURAC), 1 part by weight of ethanol (Wako Pure Chemical Industries, Ltd., special grade chemical), and 0.0042 part by weight of a dye D&C Violet NO. 2 (Spectrum Chemical MFG. Corp.) were weighed, placed into a medium bottle, and the mixture was stirred with a vortex mixer S10286 at a scale of 10 for 5 minutes. Thereafter, 8 parts by weight of dichloromethane was added, the resultant mixture was stirred with a vortex mixer S10286 at a scale of 10 for 1 minute, and stirred with a high viscosity stirrer SNF-01 at 1000 rpm for 10 minutes to obtain a uniform polymer solution for spinning was obtained.

[Spinning with Polymer Solution for Spinning]

Electrospinning was performed using the spinning solution obtained as described above. Using a double tubular nozzle having a constitution of a nozzle inner diameter of 0.47 mm and an outer ring inner diameter of 1.45 mm, and setting the number of nozzles at 12 and a pitch interval between each nozzle at 70 mm, spinning was performed with a spinning distance of 400 mm, a dope flow rate of 4 ml/h, and a spinning applied voltage of 35 kV. A collection plate 330 mm×440 mm made of SUS304 was used on a fiber collection side, and a voltage of −5 kV was applied to the collection plate. Upon spinning, 300 ml/h of the compressed air (0.3 MPa) was supplied via a 3 L closed glass container in which 500 ml of dichloromethane was enclosed beforehand, and 300 ml/h of the saturated dichloromethane vapor was supplied to each space between nozzle and outer tube. Under these conditions, even when spinning was continued for 25 minutes, no solid was generated at the nozzle tip.

COMPARATIVE EXAMPLE

Spinning was performed under the same conditions as those of the Example except that the saturated dichloromethane vapor was not supplied to the space between nozzle and outer tube at the time of spinning. Under these conditions, a solid started growing at the nozzle tip immediately after the start of spinning, and 40 seconds after the start of spinning, growth of the solid at the nozzle tip made spinning unable to continue.

INDUSTRIAL APPLICABILITY

The present invention is excellent in spinning stability and spinning yield, is also useful as a spinning method and a device capable of conducting continuous production, and is utilized, for example, in non-woven fabric manufacturing industry.

DESCRIPTION OF THE REFERENCE NUMERALS

-   1. Constant volume feeding machine -   2. Syringe -   3. Connecting hose -   4. Double tubular nozzle -   5. Connecting hose -   6. Solvent bubbling bottle -   7. Needle valve for control -   8. Volumetric flowmeter -   9. Gas supply part -   10. Supply port for raw material solution (dope liquid) -   11. Supply port for gas containing solvent vapor 

1. A nozzle device for spinning, comprising a nozzle, a polymer solution supply means for supplying a polymer solution to a nozzle to eject it from a nozzle tip, and a solvent vapor supply means for supplying a gas containing the vapor of the same solvent as a solvent of the polymer solution at least to the periphery of the polymer solution just ejected.
 2. The nozzle device for spinning according to claim 1, wherein the device has a double tubular structure part composed of an inner tube, the inner tube being a nozzle, and an outer tube surrounding it, and is configured such that a gas containing the vapor of the same solvent as the solvent of the polymer solution is supplied from a space between the inner tube and the outer tube.
 3. A method of spinning fibers containing a polymer, comprising a step of ejecting a polymer solution from a nozzle tip, wherein spinning is performed while supplying a gas containing the vapor of the same solvent as a solvent of the polymer solution at least to the periphery of the polymer solution just ejected.
 4. The spinning method according to claim 3, wherein the gas to be supplied contains a substance that is in a gaseous phase under the condition at the time of spinning, and is saturated with the vapor of the same solvent as the solvent of the polymer solution. 